1. Field of the Invention
The present invention relates to seat belt retractors, and more particularly, to seat belt retractors of a type which has both an auto-locking mode (ALM) and an emergency locking mode (ELM).
2. Description of the Prior Art
Hitherto, various types of seat belt retractors have been proposed and put into practical use particularly in the field of wheeled motor vehicles. One of them is the type disclosed in Japanese Utility Model First Provisional Publications Nos. 63-145747 and 2-2264, which has both an auto-locking mode (ALM) and an emergency locking mode (ELM). The auto-locking mode (ALM) is the mode in which once the seat belt is loosely put on the seat occupant, the belt is automatically retracted by a degree to permit a tight fitting of the belt to the belt wearer, and the feeding of the belt from the retractor is blocked. While, the emergency locking mode is the mode in which when a certain shock is applied to the retractor due to a vehicle collision or the like, feeding of the seat belt from the retractor is suppressed thereby to prevent the belt wearer from being thrown forward.
However, in the seat belt retractors of the above-mentioned double function type, there is sometime a difficulty in making a smoothed switching from the emergency locking mode (ELM) to the auto-locking mode (ALM) and vice versa. More specifically, when each part of the retractor fails to have exact dimension, the switching between the two modes is not smoothly carried out. Furthermore, due to their inherence which requires a complicated layout of parts, some of them are bulky in construction.